Flexible tubing or casing



. A 25 19 A. A. BUFFET,

2,649,778 FLEXIBLE TUBING OR CASING Filed July 29, 1947 INVENTOR. ART/1w? 4/1/0195 Bar/5r ATTORNEX Patented Aug. 25, 1953 FLEXIBLE TUBING OR CASING Arthur Andr Buifet, Bondy,

France, assignor to Etablissements Marret, Bonnin, Lebel & Guieu,

Paris, France Application July 29, 1947, Serial No. 764,331 In France November 14, 1939 Section 1, Public Law 690, August 8, 1946 Patent expires November 14, 1959 1 Claim.

It is known that flexible tubings or casings may be formed by winding one or more metal strips of appropriate shape.

Known types of flexible tubing have, however, several disadvantages, particularly low tensile and bending strengths.

When the stresses imposed on the tubing are too high, the shaped metal strips are distorted and become disengaged from one another.

In addition, the strips may also become disengaged if the tube is bent in a sharp arc, even though gradual stress is applied.

It is the object of the present invention to provide a flexible tubing or casing which overcomes such drawbacks.

The flexible tubing or casing of the invention comprises helically wound metal bands of generally U-shaped cross section with the edge portions of the bands folded back upon themselves to form hooks transversely of the tube. The tube so constructed has high tensile and bending strengths.

Other objects of the invention will be apparent from the following detailed description and from the drawings, wherein Fig. 1 is a perspective view of a metal tubing constructed in accordance with and illustrating one embodiment of the invention;

Fig. 2 is a longitudinal sectional view of the tube shown in Fig. 1;

Fig. 3 is a longitudinal sectional view of another embodiment of the invention;

Fig. 4 is a sectional view of the tube showing one step in assembling it in accordance with the invention; and

Fig. 5 is a similar view showing another assembling step.

In the embodiment shown in Figs. 1, 2, 4 and 5, the tube comprises two channel-shaped bands helically wound one upon the other, with the channels facing each other in such manner that the flanges c of the band a embrace two flanges d of the band I) and conversely.

The flanges c and d of the bands a and b terminate in hooks e and j which are mutually engaged. Very high tensile and bending strengths are thus conferred to the tube, owing to the fact that when the tube is bent, the hooks tend to engage one another more closely. The tube may be bent in very sharp arcs without the risk of the bands becoming disengaged from one another or the section of the tube becoming flattened or distorted.

The tube shown in Fig. 3 difiers from that shown in the other figures of the drawing in the rounded form of the outer band a. It will be understood that other like variations are also possible.

The flexible tubes of the invention may be lightly enclosed or insulated by means of a yieldable auxiliary tube or casing suitably formed from an impervious or insulating substance and placed over or in the main flexible tube. For instance, the flexible tube shown in Fig. 3 may be provided with an inner rubber tube 2.

In addition, for the purpose of making them impermeable or insulated, the flexible tubes may be coated or varnished.

The method for preparing the tubes is diagrammatically shown in Figs. 4 and 5. The bands are provided with hooks e and j which are only partially formed. They are wound on a core 9, which step is shownpin Fig. 4.

The tube, as shown in Fig. 5, is then pressed between the core 9 and a surface such as h; the hooks e of the flanged band b contact the bottom surface of the band a and conversely the hooks f of the band a contact the bottom surface of the band b; the hooks are thus closed under pressure and interlocked.

The tubing or casing of the invention may have numerous applications, e. g. as a control cable, a casing for electric conductors, as flexible piping for lubrication, etc.

I claim:

In a tube or flexible sheath, a first band of generally U-shape cross section Wound into a helix, the legs of the U projecting radially outwardly and being defined by the edge portions of the band folded back upon themselves so as to form hooks transversely of the tube, a second band of similar configuration having the legs of the U projecting radially inwardly, said second hand being spirally wound on said first band, whereby said legs of the second band engage With their hooked ends the corresponding portions of two consecutive turns of said first band.

ARTHUR ANDRE BUFFET.

References Cited in the file of this patent UNITED STATES PATENTS 

